1. Field of the Invention
The present invention relates to a multi-chamber treatment system provided with a plurality of vacuum process chambers for treating objects to-be-treated, such as semiconductor wafers, LCD substrates, etc., and more particularly, to a multi-chamber treatment system for executing a normal-pressure treatment as a pre- or post-treatment for a reduced-pressure treatment.
2. Information of the Related Art
Recently, various semiconductor manufacturing processes have been contrived to tackle the development of finer, higher-integration versions of semiconductor devices. As vacuum treatment systems for semiconductor wafers, for example, multi-chamber treatment systems called cluster tools or the like have been developed such that a plurality of vacuum process chambers are arranged circumferentially to cope with reformation or modification of various processes easily and shorten the processes through the execution of integrated treatments.
One such conventional multi-chamber treatment system is provided with a required number of vacuum process chambers (supposedly three to six in number, for example) which correspond individually to various semiconductor manufacturing processes. A transportation system for loading into or unloading an object to-be-treated from the individual vacuum process chambers comprises one or two load-lock chambers, a polygonal transfer chamber, and a rotatable contractible transfer arm (transfer robot) in the transfer chamber. The peripheral wall of the transfer chamber is formed with a plurality of junction ports which communicate airtightly with the surrounding vacuum process chambers and load-lock chambers by means of gate valves, individually.
In the multi-chamber treatment system of this type, objects to-be-treated, such as semiconductor wafers (hereinafter referred to simply as wafers) stored in a cassette, are carried into each of the load-lock chambers by means of an external transportation apparatus. Then, the gate valve of the load-lock chamber on the transfer chamber side is opened after the load-lock chamber is evacuated or loaded with an inert gas for replacement so that it is isolated from the outside. The wafers are fetched one after another from the cassette in the load-lock chamber into the transfer chamber by means of the transfer arm, and are transferred successively into the vacuum process chambers. Then, predetermined treatments, such as filming, etching, etc., are executed, and the treated wafers are taken out into the transfer chamber and returned to the cassette in the load-lock chamber by the transfer arm.
In the multi-chamber treatment system arranged in this manner, the load-lock chambers, transfer chamber, and transfer arm, which constitute the transportation system, can be used in common for the vacuum process chambers which are arranged circumferentially. As compared with a conventional treatment apparatus which includes transportation systems provided individually for the vacuum process chambers, therefore, the multi-chamber treatment system is very advantageous, enjoying a simpler configuration, reduced installation space, and improved transportation efficiency.
According to the conventional multi-chamber treatment system, however, a necessary number of vacuum process chambers are selected and provided individually for various processes in compliance with users' requests. A transfer chamber with a suitable shape and size is manufactured in consideration of interfaces with the vacuum process chambers on the basis of the shape and size of the process chambers, and the process chambers are fixedly arranged around the transfer chamber so as to communicate airtightly therewith by means of the gate valves, individually. The load-lock chambers are attached to an end portion (loading portion side) of the peripheral wall of the transfer chamber. The system is completed by setting the transfer arm in the transfer chamber. The transfer arm has a minimum radius of rotation such that it can rotate in the transfer chamber and a maximum arm reach such that each wafer can be transferred from the transfer chamber into the vacuum process chambers and the load-lock chambers.
In order to construct a multi-chamber treatment system in which the number of vacuum process chambers varies with the change of processes, therefore, the transfer chamber should naturally be remade for a shape and size suited for the arrangement. It is necessary, however, to remake the load-lock chambers so that they can be connected to the transfer chamber, and to assemble the transfer chamber with the minimum radius of rotation and maximum arm reach suited for the transfer chamber. In other words, the transfer chamber, transfer arm, and load-lock chambers, which constitute the transportation system, must all be remade and assembled for each process at a user's request, so that the design and manufacture of the transportation system entail troublesome operations and increase in cost on each occasion.
In using the multi-chamber treatment system thus constructed for each process, moreover, it is necessary to move the transfer arm in the transfer chamber and teach and store a program control unit with an object transportation route and distance, since the vacuum process chambers vary in shape and size. These operations are troublesome, and triggering the system operation requires much time.
As is generally known, the manufacture of semiconductors requires many processes, and some other treatment processes are executed before and after a reduced-pressure treatment.
In many cases, a treatment in a reduced-pressure treatment apparatus requires, as its pre- or post-treatment, a so-called normal-pressure treatment which is conducted under atmospheric pressure. In some cases, for example, a treatment in a reduced-pressure ambient gas may be preceded by a cleaning process for removing impurities, which are caused to adhere to the object surface in the preceding treatment process, and a drying process.
Usually, in the cleaning and drying processes, a plurality of wafers in each cassette are batch-processed simultaneously by means of cleaning and drying devices. Then, the cleaned and dried wafers are handled in each cassette and transferred from the cleaning and drying devices into the reduced-pressure treatment apparatus.
The cleaning and drying devices for the aforesaid pretreatment are separated spatially and temporally from the reduced-pressure treatment apparatus for the post-treatment. Accordingly, a time interval for transportation, standby, etc. is required between the pre- and post-treatments. Although the to-be-treated objects are cleaned and dried with trouble, therefore, impurities in the atmosphere will inevitably adhere to the object surface. Conventionally, in other words, the reduced-pressure treatment in the next stage cannot be started without changing the state immediately after the normal-pressure treatment.
Depending on the kind of the normal-pressure treatment, moreover, the semiconductor wafers may be treated one by one in sheet form, so that normal-pressure sheet-form treatments may possibly increase with the development of finer treatments. In this case, the handling frequency for wafers to be loaded into and unloaded from each cassette increases. If the handling frequency increases in the course of a series of semiconductor manufacturing processes, problems are aroused including lowering of the yield by dusting which is attributable to mechanical contact with the wafers, as well as reduction of the throughput and waste of driving energy.